Updating Parent ZonesInternet Systems Consortium950 Charter StreetRedwood CityCA94063USmarka@isc.org
DNS UPDATE was developed to allow DNS zones to be updated.
There is a perception that UPDATE cannot be used in conjuction
with the Registry, Registar, Registrant (RRR) model to update a zone.
This document explains how UPDATE can be used in the RRR model.
UPDATE is designed to update any
zone in the DNS. This includes updating delegating NS
records, glue address records and DS records.
While UPDATE is primarily designed to UPDATE a zone directly
there in no reason why UPDATE requests cannot be translated
to the EPP requests to perform the changes.
This would provide a uniform model to update parent zone
regardless of where they are in the DNS hierarchy or whether
the zone is signed or not.
This document was written with the following requirements in
mind:
must be able to authenticate the transaction.must be able to update address records to support automated
renumbering.must be able to update DS records to support DNSKEY rollover
buy key management tools.must work for unsigned zones (parent and/or child).must work for signed zones (parent and/or child).must work for RRR managed zones.must work for non RRR managed zones.desirable support updating of NS RRsets so that nameservers
can ensure delegations delgation data remains consistent.
The Registrar would host a server that authenticates UPDATE
requests received directly or relayed by the Registry using
TSIG , then translate the actions
in the UPDATE request into EPP transaction requests. The
results of those EPP transactions would be relayed to the
UPDATE client.
Requests that are not TSIG signed or fail verification must
be rejected.
The translating server would handle a restricted subset of
UPDATE requests, possibly ignoring the prerequiste section.
UPDATE requests would be limited to those supported by EPP.
e.g. Add NS record. Delete all NS records. Add A record.
Delete AAAA record. Add DS record. Delete DS record.
The translating server may also override/ignore the TTL in
the UPDATE request.
Authentication would be done using TSIG. TSIG was designed
to be used in a environment where requests are relayed.
Authentication can be done down to the <NAME,TYPE>
tuple. There exist nameservers that already implement
access contols down to this level of granularity based on
the presented TSIG.
This would allow nameservers to update their own address
records as they get renumbered without being able to update
anything else.
This would allow DNSSEC key management software to update
DS records without being able to update anything else.
As Registrars do all the authentication and generate the
signed responses there is no need for the Registry to have
access to the private key material used in TSIG.
Registrars already handle shared keys in these numbers with
their web interfaces so it is not unreasonable to expect
them to be able to handle a similar number of shared TSIG
keys.
The hardest part of Direct to Registrar is finding where
to send the UPDATE request. This would most probably just
be advised to the Registrant.
In the indirect model the Registry would host a UPDATE relay
server which would examine the first record of the UPDATE
section and relay the request to the Registrar of record
for the owner name of that record. The Registrar would
verify the validity if the request based on the TSIG then
update the registry contents using EPP if appropriate. The
response from the Registrar would be relayed back to the
client via the Registry.
The Registry takes no action other than to relay the request
and response unless it is directed to do so by the Registrar.
The relay can use either TCP or UDP when forwarding UPDATE
requests as TSIG supports changes to the DNS id field when
a request/response is relayed. Only the Registrar and the
client (Registrant) need to know the TSIG secret.
This is consistent with how tools like nsupdate work out
where to send a UPDATE request if the zone is not explicity
set. They look at the ownername of the first record and
use it to discover the containing zone.
UPDATE server discovery is a issue when the RRR model is
in use as the UPDATE may need to be directed through EPP
and/or sent to a Registrar. There are a number of way this
could be done:
1) Adding a underscore infix labels to the zone which contain
SRV records at pointing to Registar/Registry servers for
each child.
e.g. <child>._update._tcp.<parent> SRV 0 0 53
server.example.tld
The server pointed to could be be a relay server, as described
above, or a UDPATE to EPP translating server. A relay
server would allow for slower zone growth.
Using underscore infix labels requires no changes to
nameservers operated by Registries but does require the
zone content to be updated or a separate zone (e.g.
_update._tcp.<parent>) to be delegated to contain
this information.
A level of indirection could be added by using CNAME records
to point to a domain operated by the registrar which contains
the SRV record. This would allow the registrar to update
the SRV records without having to update the zone being
served by the registry. The CNAME would be updated on
registrar changes. Note the target name the CNAME could
also be managed by the registry as a way to consolidate the
SRV record management.
As with traditional use of SRV, non-support can be signaled
with
If the Resistry is operating a relay this can be supported
with a single wildcard record.
The client can fallback to direct update to parent servers
if no SRV record is discovered. This allows the scheme to
work outside of the registry, registrar, registant model.
2) Extend UDPATE to return the update server. Currently
the Zone section of the UPDATE refers to the zone to be
update and is identified by the <QNAME,SOA,QCLASS>
tuple. Replacing SOA with one or more of DS, NS, A and
AAAA would allow a nameserver to distingish between a
traditional UPDATE request and a request to find the UPDATE
servers. The tuple would contain the resource to be updated
and the reply would contain SRV records pointing to the
UPDATE servers. As there would possibly more than one
parent the owner records would refer to the parent zone
being updated.
The UPDATE requests are all TSIG signed. This is a proven method
for securing UPDATE requests in the DNS.
Dynamic Updates in the Domain Name System (DNS UPDATE)Secret Key Transaction Authentication for DNS (TSIG)